1. Field of the Invention
The present invention relates to a semiconductor device having a structure in which an InGaP layer and a GaAs layer are stacked.
2. Description of Related Art
A module on which power amplifier elements and switch elements are mounted has been developed for reducing size and achieving multi-function in an IC for wireless communication of mobile terminal. Enhancement-type FETs are used as power elements due to the requirement of an operation with a single power supply. On the other hand, as switch elements, depletion-type FETs that can easily realize a low on resistance are used. Techniques are implemented in which those two elements are prepared on the same single substrate to form power amplifier elements and switch elements on one chip.
In order to achieve the structure described above, there is a method in which a plurality of etching stopper layers are used to arrange an FET gate at different distances from a channel layer. The InGaP layer serves as a stopper layer against a sulfuric acid etchant for etching GaAs and AlGaAs. Such etching is performed by means of wet etching. The wet etching has an advantage that a crystal suffers less damage compared to the dry etching.
The list below is conventional arts the applicant found:    Patent Document 1: Japanese Laid-Open Patent Application JP-P2004-179318A;    Patent Document 2. Japanese Laid-Open Patent Application JP-P1993-259191A;    Patent Document 3; Japanese Laid-Open Patent Application JP-P1994-244218A;    Patent Document 4; Japanese Laid-Open Patent Application JP-P2004-158772A;    Non-Patent Document 1: T. Tanaka, K. Takano, T. Tsuchiya and H. Sakaguchi, “Ordering-induced electron accumulation at GaInP/GaAs hereto-interfaces”, Journal of Crystal Growth, December 2000, Volume 221, p. 515-519; and    Non-Patent Document 2; K. Yamashita, K. Oe, T. Kita, O. Wada, Y. Wang, C. Geng, F. Scholz and H. Schweizer, “Electronic Structure of ordered. Ga0.5In0.5P/GaAs Heterointerface Studied by Raman-Scattering and Photoluminescence-Excitation Measurements”, Japanese Journal of Applied Physics, Volume 44., p 7390-7394.